/**
 * @file config.c
 * @brief NVS Configuration Management
 */

#include <string.h>
#include "config.h"
#include "nvs_flash.h"
#include "nvs.h"
#include "esp_log.h"

static const char *TAG = "nexus_config";

/* NVS namespace */
static const char *NVS_NAMESPACE = "nexusguard";

/* NVS keys (all < 15 chars per NVS limit) */
static const char *KEY_DEVICE_ID     = "device_id";
static const char *KEY_PRIVATE_KEY   = "private_key";
static const char *KEY_PRESHARED_KEY = "preshared_key";
static const char *KEY_INTERNAL_IP   = "internal_ip";
static const char *KEY_SERVER_PUB    = "server_pub";
static const char *KEY_ENDPOINT      = "endpoint";
static const char *KEY_DNS           = "dns";
static const char *KEY_ALLOWED_IPS   = "allowed_ips";
static const char *KEY_SERVER_WG_IP  = "server_wgip";
static const char *KEY_CONFIG_HASH   = "config_hash";

/* NVS handle (open once, reuse) */
static nvs_handle_t s_nvs_handle = 0;
static bool s_nvs_open = false;

/**
 * @brief Helper: write string to NVS
 */
static esp_err_t nvs_write_str(const char *key, const char *value)
{
    if (!s_nvs_open) {
        return ESP_ERR_INVALID_STATE;
    }
    esp_err_t err = nvs_set_str(s_nvs_handle, key, value);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to write NVS key '%s': %s", key, esp_err_to_name(err));
    }
    return err;
}

/**
 * @brief Helper: read string from NVS into buffer
 */
static esp_err_t nvs_read_str(const char *key, char *buf, size_t buf_len)
{
    if (!s_nvs_open) {
        return ESP_ERR_INVALID_STATE;
    }
    size_t required_size = 0;
    esp_err_t err = nvs_get_str(s_nvs_handle, key, NULL, &required_size);
    if (err != ESP_OK) {
        return err;
    }
    if (required_size > buf_len) {
        ESP_LOGE(TAG, "NVS key '%s' value too large (%zu > %zu)", key, required_size, buf_len);
        return ESP_ERR_NVS_INVALID_LENGTH;
    }
    err = nvs_get_str(s_nvs_handle, key, buf, &buf_len);
    return err;
}

esp_err_t config_init(void)
{
    ESP_LOGI(TAG, "Initializing NVS config module...");

    esp_err_t err = nvs_open(NVS_NAMESPACE, NVS_READWRITE, &s_nvs_handle);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to open NVS namespace '%s': %s", NVS_NAMESPACE, esp_err_to_name(err));
        return err;
    }
    s_nvs_open = true;

    ESP_LOGI(TAG, "NVS config module initialized");
    return ESP_OK;
}

esp_err_t config_save(const wg_config_t *config)
{
    if (config == NULL) {
        return ESP_ERR_INVALID_ARG;
    }

    ESP_LOGI(TAG, "Saving config for device: %s", config->device_id);

    esp_err_t err;
    esp_err_t final_err = ESP_OK;

    err = nvs_write_str(KEY_DEVICE_ID, config->device_id);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_PRIVATE_KEY, config->private_key);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_PRESHARED_KEY, config->preshared_key);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_INTERNAL_IP, config->internal_ip);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_SERVER_PUB, config->server_pub);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_ENDPOINT, config->endpoint);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_DNS, config->dns);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_ALLOWED_IPS, config->allowed_ips);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_SERVER_WG_IP, config->server_wg_ip);
    if (err != ESP_OK) final_err = err;

    err = nvs_write_str(KEY_CONFIG_HASH, config->config_hash);
    if (err != ESP_OK) final_err = err;

    if (final_err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to save config");
        return final_err;
    }

    /* Commit to flash */
    err = nvs_commit(s_nvs_handle);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to commit NVS: %s", esp_err_to_name(err));
        return err;
    }

    ESP_LOGI(TAG, "Config saved successfully");
    return ESP_OK;
}

esp_err_t config_load(wg_config_t *config)
{
    if (config == NULL) {
        return ESP_ERR_INVALID_ARG;
    }

    /* Zero out the struct first */
    memset(config, 0, sizeof(wg_config_t));

    ESP_LOGI(TAG, "Loading config from NVS...");

    esp_err_t err;
    esp_err_t final_err = ESP_OK;

    err = nvs_read_str(KEY_DEVICE_ID, config->device_id, sizeof(config->device_id));
    if (err != ESP_OK) {
        ESP_LOGW(TAG, "No device_id in NVS (first boot?)");
        return err;
    }

    err = nvs_read_str(KEY_PRIVATE_KEY, config->private_key, sizeof(config->private_key));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_PRESHARED_KEY, config->preshared_key, sizeof(config->preshared_key));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_INTERNAL_IP, config->internal_ip, sizeof(config->internal_ip));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_SERVER_PUB, config->server_pub, sizeof(config->server_pub));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_ENDPOINT, config->endpoint, sizeof(config->endpoint));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_DNS, config->dns, sizeof(config->dns));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_ALLOWED_IPS, config->allowed_ips, sizeof(config->allowed_ips));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_SERVER_WG_IP, config->server_wg_ip, sizeof(config->server_wg_ip));
    if (err != ESP_OK) final_err = err;

    err = nvs_read_str(KEY_CONFIG_HASH, config->config_hash, sizeof(config->config_hash));
    if (err != ESP_OK) final_err = err;

    if (final_err != ESP_OK) {
        ESP_LOGW(TAG, "Config loaded with errors");
        return final_err;
    }

    ESP_LOGI(TAG, "Config loaded successfully for device: %s", config->device_id);
    return ESP_OK;
}

esp_err_t config_clear(void)
{
    ESP_LOGI(TAG, "Clearing all NexusGuard NVS keys...");

    if (!s_nvs_open) {
        return ESP_ERR_INVALID_STATE;
    }

    esp_err_t err;
    esp_err_t final_err = ESP_OK;

    err = nvs_erase_key(s_nvs_handle, KEY_DEVICE_ID);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_PRIVATE_KEY);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_PRESHARED_KEY);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_INTERNAL_IP);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_SERVER_PUB);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_ENDPOINT);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_DNS);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_ALLOWED_IPS);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_SERVER_WG_IP);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    err = nvs_erase_key(s_nvs_handle, KEY_CONFIG_HASH);
    if (err != ESP_OK && err != ESP_ERR_NVS_NOT_FOUND) final_err = err;

    /* Commit erases to flash */
    err = nvs_commit(s_nvs_handle);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to commit NVS erase: %s", esp_err_to_name(err));
        return err;
    }

    ESP_LOGI(TAG, "Config cleared");
    return final_err;
}

bool config_is_valid(const wg_config_t *config)
{
    if (config == NULL) {
        return false;
    }

    /* device_id and private_key must be non-empty */
    if (strlen(config->device_id) == 0) {
        return false;
    }
    if (strlen(config->private_key) == 0) {
        return false;
    }

    return true;
}